This invention relates to a circuit configuration for an automotive vehicle brake system with electronic anti-lock control. The circuit configuration includes circuits for individually controlling the braking pressure in the wheel brakes of the two wheels of one axle as a function of the rotational behavior of the wheels measured by wheel sensors. The circuit configuration also includes circuits for limiting the yawing moment due to braking pressure differences at the wheels of one axle, by maintaining the braking pressure differences below a permissible pressure difference being variable as a function of the friction value difference at the two wheels.
A similar circuit configuration has been disclosed by DE 39 25 828 A1 (German Patent Application). This patent application discloses an anti-lock control system with individual control of the braking pressure at the two wheels of one axle. In order to limit the yawing moment on road surfaces with very different friction values on the right and left sides, i.e., with .mu.-split conditions, the pressure difference is limited and, in doing so, the permissible pressure difference is determined as a function of the friction value difference and on the amount of the lower friction value. If this permissible pressure difference is exceeded, pressure will be reduced at the high-value wheel in consideration of the kinetic state of the low-value wheel. In order to determine the permissible pressure difference, in this known anti-lock control system, the pressure metered in by the driver will be measured on the right and left wheels and in either case the nominal pressure will be compared with the actual pressure. The friction value (i.e. friction coefficient) is assessed as a function of the braking pressure. If a predetermined pressure difference is exceeded, braking pressure will be reduced at the high-value wheel, namely at the higher-pressure wheel.
From the aforementioned German Patent Application and from DE 28 51 107 C2 (German Patent Application), it is also already known to perform the pressure reduction for the sake of limiting the yawing moment when, at the end of a control cycle, the low-value wheel again reaches the stable range.
The expenditure for individually measuring braking pressure at each wheel, and evaluating and monitoring the measured results, is significant.